Sterling water treatment plant 95% complete

Reverse osmosis to start in late February

Workers at the new Sterling Water Treatment Plant monitor every aspect of the treatment process through a monitor in their control room. (David Martinez/Journal-Advocate)

STERLING -- Inside Sterling's new water treatment plant is a cacophony of humming pumps and buzzing electronics, accompanied by a maze of multi-colored pipes, filters and boxes scattered through what looks like an open concrete warehouse.

The engineers at the plant are quick to point out the two years of construction work it took to get the plant to where it is -- the millions of city tax dollars spent.

But by the end of February, they say, 80 percent of the city's water will run through dozens of stacked reverse osmosis (RO) filters, squeezing out pollutants to meet state standards.

"It's not something you call in and say, 'Hey, deliver this to us,'" said Mark Youker, construction manager for Hatch Mott McDonald, which has overseen the architecture and engineering of the project. "It's a lot more complicated than that."

Plans to build the plant started around September 2008, when the Colorado Department of Public Health and Environment issued an enforcement order to get the city's water standards up to compliance within a given time frame. The main contaminant, among others, was the water's naturally-occurring uranium levels, which could increase an individual's cancer risks over longer exposures.

Youker said before the plant was constructed, Sterling's water was pumped directly from wells across the county, treated with chlorine at four separate stations and delivered directly to city homes, farms and businesses.

When the plant becomes fully operational, the city's raw well water will all instead flow straight to the one spot for treatment.

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It's capable of providing 9.5 million gallons of water to the city per day, though the average demand is only about 4 million gallons.

The water will run through a filtration system before it's chlorinated, and be pumped out as a 80/20 mix of RO-treated to untreated water; Youker said the city has been receiving the "20 percent," filtered water for about two months already.

Ryan Walsh, the project engineer, said the mix holds several structural and taste benefits.

Workers at the new Sterling Water Treatment Plant monitor every aspect of the treatment process through a monitor in their control room. (David Martinez/Journal-Advocate)

"The first goal (of treatment) is to bring the city's water to compliance with the new state standards," Walsh said. "The second is to bring water that more aesthetically pleasing and requires less maintenance."

He said the RO also filters out essential minerals from the water, which negatively affects the taste. Youker added that treating all of the city's water with RO would have presented a cost issue and that it would have been "nearly impossible" to get out all of the water's uranium.

Getting Sterling softer, purer water circulating will create some issues that are difficult to predict, however.

For example, the new water quality is expected to cause some issues with the city's water lines, as it erodes some of the old mineral deposits in the city's pipes.

Public Works Director Jim Allen said the change will cause discoloration in the water for a brief period of time after it enters the system, though he couldn't predict how long that would be an issue.

The erosion might cause some of the city's older or more fragile pipes to burst, as well -- an issue Allen said would be difficult to predict or prevent ahead of time. Proactively replacing the city's water pipelines would be too costly for the city.

"The city's going to deal with it as it comes," Allen said.

It's hard to predict just how long it would take for the newly filtered water to reach Sterling's water users. The water first has to flow through the plant to two water tanks and two water towers around the city, replace the existing water and flow back out.

Once the water starts flowing, the water plant's next goal is to finish its deep injection wells where it will send its "concentrate," or the waste filtered from the well water.

Youker said the well has already been dug 7,000 feet underground, below the city's existing wells and under a protective layer of granite. The city just has to finish the pumping mechanisms to transport the up to 200,000 gallons per day of concentrate from the plant to the well.

But even when that's complete, the plant will have constant supervision from the city. The RO filters need replacing every three to six months, and the system needs constant monitoring and testing to ensure the city receives no more or less water than it needs and that its quality doesn't falter.

In the coming week, though, Youker said employees will start testing all of the water plant's systems and perform minor additions and changes. The tests take about a month to complete.

But Youker and Allen said the updates will come soon and become more public as the plant becomes more functional.

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